[Magee]

I have a similar problem with the back case on my AU 1 Heater control. The plastic mount that holds the cable had broken away due to brittleness. When you turn the temp knob it had no effect as the cable was floating.

Being an older guy I went for an old school solution and made a bracket out of 2 pieces of sheet metal that I could screw to the back of the heater control unit as the picture. Needed to do some fine tuning to ensure it mated to the back case and also did not foul with anything in the dash when fitted.

It looks a bit rough, but since it is not visible when fitted I was okay with it and I know it is lot stronger than the original design of a barbed clip into the plastic square hole.